1. Field of the Invention
This invention relates generally to logging equipment, more particularly to a radio-controlled, slack-pulling skyline carriage.
2. Related Art
In reviewing the body of patents and commercial products that incorporate controls to skyline carriage type vehicles, none of the information reveals a similar closed-loop method of controlling the position of the carriage, nor providing controls that facilitate the types of operations of which this invention is capable.
A distinct advantage of the closed-loop operation method of the present invention lies in its ability to control the effective load and speed (RPM) of the driving engine under differing conditions to best make use of its engine braking, power and torque characteristics. As will be made evident in the description that follows, based upon monitoring engine RPM, the control system proportionally controls the main hydraulic pump output volume to keep the engine running within its optimal RPM band. Due to the utility of the closed-loop control system, as set forth in the present invention, the general carriage operation in timber harvesting via remote control is far easier compared to other carriages presently known in the art.
In earlier inventions, a variety of skyline carriages were patented; each of them different in various key aspects from the present invention. Gauthier in U.S. Pat. No. 5,020,443 teaches about a radio-controlled carriage that houses an internal combustion motor and a drive system that provides a driving method and hoist method that is fundamentally different than the current invention in that it has a driven set of mainline pulleys, whereas the mainline pulleys of the present invention are free rolling.
In U.S. Pat. No. 4,687,109, Davis describes a carriage that uses batteries, motors and a skyline powered recharging method to move and brake the carriage. This approach, versus the current invention, is fundamentally different in providing only a limited ability to pull large loads with the skidline. It relies upon an electrical power source that charges/stores energy from movement of the carriage along the skyline.
In U.S. Pat. No. 4,515,281, Maki teaches about a system whereby the movement of the carriage along the skyline drives two on-board hydraulic pumps and a large accumulator that power the skidline sheave. This approach requires multiple pumps, clutches and mechanisms to realize motive power for the skidline sheave, and relies on the energy that is provided by movement of the carriage along the skyline. There are multiple shortcomings to the invention as it is described, all of which are overcome with the present invention. The primary problem with Maki's invention is its reliance upon carriage motion for operation of the skidline sheave. Pump selection and drive ratios are problematic in that the slope of the cable, which varies from site to site, must be considered in selecting the configuration of the pump drivetrain components.
As will be seen in the description that follows, the present invention is a more efficient and useful device than all prior art.